glMapGrid and glEvalMesh are used in tandem
to efficiently generate and evaluate a series of evenly spaced map domain
values. glEvalPoint can be used to evaluate a single grid point in the same
gridspace that is traversed by glEvalMesh. Calling glEvalPoint1 is equivalent
to calling

glEvalCoord1( i$^cdot^DELTA u ~+~ u sub 1$ );where

$DELTA u ~=~ ( u sub
2 - u sub 1 ) ^/^ n$

and $n$, $u sub 1$, and $u sub 2$ are the arguments
to the most recent glMapGrid1 command. The one absolute numeric requirement
is that if $i~=~n$, then the value computed from $i ^cdot^ DELTA u ~+~ u
sub 1$ is exactly $u sub 2$.